These were the least expensive large envelopes available at Staples. Since I needed to have 30 envelopes to send information to every family in my classroom I was interested in saving some money. Unfortunately these envelopes were simply a bad choice. In short the adhesive strip is worthless. They don't stay sealed while stacked in a box waiting to be distributed. There is no possibility that they would ever survive a trip through the mail. It was necessary to seal every envelope with package-sealing tape. The additional cost for the tape (along with the extra time) made this "lowest cost" alternative the worst choice.